Conventional twin-roller casting apparatus usually have radii (R) of greater than or equal to 50 cm and the pool of molten metal typically has a depth h.gtoreq.2/3R.gtoreq.33 cm. Containment of the molten metal pool sidewalls, particularly at the rollers, is preferably accomplished using magnetomotive forces. Most of the magnetomotive force for containment of each sidewall is required at a pool depth approximately 25% below the pool surface. The magnetomotive force required for sidewall containment at that depth can be three times larger than what is required at the bottom of the pool because the flux path length is much larger than the path at the bottom of the pool. These large magnetomotive force forces require relatively large power supplies (e.g., .gtoreq.500 kW) and the power losses in the sidewall of the pool of molten metal and in the magnet are correspondingly large. These power losses have been found to cause undesirable heating of the molten metal.
Accordingly it is an object of the present invention to provide an improved method and apparatus for reducing the magnetomotive force for sidewall containment when casting metal sheets.
It is another object of the present invention to provide a novel apparatus and method for containing a pool of molten metal comprising a shaped horizontal alternating magnetic field and a mechanical dam.
It is a further object of the present invention to provide an improved method and apparatus for preventing a pool of molten metal from flowing over the ends of counter-rotating rollers comprising a shaped horizontal alternating magnetic field and a ferromagnetic dam.
It is a further object of the invention to provide a novel method and apparatus that contains molten metal with a minimum of power dissipation in sidewalls of the molten metal.
It is a still further object of the invention to provide an improved method and apparatus that contains a pool of molten metal from flowing out sides of a containment means with a minimum of electrical power consumed by the containment means.
The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements.